A former Grey’s Anatomy star is swooping in as Supergirl's big sis! TV Line reports that Chyler Leigh has joined the upcoming CBS superhero series as Alex Danvers, Kara’s foster sister whose longtime fascination with her sister’s powers inspired her to become a doctor. Yes, you heard that right — the onetime Grey’s surgeon will be playing a doctor yet again. Are you excited to see Chyler scrub in as Melissa Benoist’s big sis? Or will she always be “Lexi” to you? Sound off in the comments and stick with us at Celebified for more TV scoop.